1. Technical Field
The present invention relates to a mounting apparatus and method for mounting semiconductor components, more particularly, to a mounting apparatus and method for mounting photonic components in die form on substrates with high positional accuracy.
2. Discussion of the Related Art
Efforts to perfect precise positioning of small semiconductor devices onto a substrate have received considerable attention over the past few years. Tools for this purpose generally employ a digital camera, machine vision software, and stepper motors with encoders capable of sub-micron resolution in motion control. FIG. 1 illustrates a prior art metal bond head 100 with a single vacuum hole 101 typically used to lift a die 103 from its center. In order to leave the fiducials 104 of the die 103 exposed for viewing by a digital camera, this bond head 100 must be significantly smaller than the die 103. The position of the die fiducials 104, obtained with sub-micron precision using pattern recognition software, are compared to the position of fiducials on a substrate. This information is used to determine how far the stepper motors must move to accurately position the die 103 on the substrate. Once positioned, epoxy is used to attach the die 103 to the substrate and the epoxy is cured.
For extremely small die, e.g. 200–300 micron on edge, use of a metal bond head is problematic because of the requirement that the bond head be much smaller than the die so that the fiducials remain exposed. One example of a prior approach uses a see-through (ST) bond head 200 made of glass which solves this problem (see FIG. 2). The ST bond head 200 in this case allows a downward viewing camera to see the fiducials 104 while simultaneously keeping the bond head 200 larger than the die 103. The restriction on this head is less severe because only the vacuum hole 201 must be much smaller than the die 103, not the entire bond head 200.
For instance, U.S. Pat. Nos. 5,018,936 and 5,033,783 disclose one type of mounting apparatus equipped with a mounting head, which is provided with a suction nozzle assembly at one end thereof, and a recognition camera, which is mounted above the mounting head opposite the suction nozzle assembly. The suction nozzle assembly is adapted to pick up electronic parts and is made from a light transmitting material such that the picked-up parts can be viewed by the camera through the suction nozzle assembly for determining their shape and position. In this manner, the mounting apparatus eliminates the need to provide a camera adapted to be positioned below the suction nozzle assembly for viewing the images of the picked-up parts.
The mounting apparatus described above has various shortcomings and disadvantages. For instance, the mounting apparatus is not adapted for precise placement of microscopic objects, such as semiconductor components, on other objects (e.g., such as substrates). Moreover, because the camera is not incorporated into the mounting head, the camera needs to be mounted to the mounting apparatus separately from the mounting head, thereby requiring an additional effort to mount the camera to the mounting apparatus and then to align the camera with the mounting head. Further, because the suction nozzle assembly is mounted to the mounting head via a retainer member, detachment of the suction nozzle assembly from the mounting head involves removal of the retainer member from the suction nozzle assembly.
U.S. Pat. No. 6,203,082 to Bendat, et al. addresses some of the disadvantages and shortcomings of the method discussed above by providing an improved mounting apparatus for serially picking up and precisely placing microscopic devices, such as semiconductor devices and optoelectronic dies, to other semiconductor devices (e.g., substrates). Referring to FIGS. 3A and 3B, the mounting apparatus 4010 includes a mounting head 4200 with an attached upper chuck 4056 and a suction-operated engagement nozzle 4058 for selectively gripping a semiconductor component or die positioned adjacent one side of the engagement nozzle 4058. A suction-operated attaching mechanism is also provided for selectively and removeably attaching the upper chuck 4056 to the mounting head 4200 of the mounting apparatus 4010, whereby the upper chuck 4056 is removable from the mounting head 4200 and is hence replaceable. The mounting apparatus 4010 also has a viewing mechanism, including a camera 4082, for viewing an object gripped by the engagement nozzle 4058. The camera 4082 is located in a horizontal plane and utilizes a mirror 4176 to look down on the engagement nozzle 4058. The upper chuck 4056 has a light-transmitting portion positioned in such a manner that an object gripped by the engagement nozzle 4058 may be viewed by the camera 4082 through the upper chuck 4056.
While the various mounting apparatus described above overcomes the disadvantages of using a metal bond head, they do not address the problem of placing several die at once with high precision. The mounting apparatus described above place die serially, one die at a time, i.e., aligning the bond head with die, moving from the die storage location to the substrate, dispensing epoxy, placing the die, and curing the epoxy for each die placed. However, if all the die could be loaded onto the bond head with high precision, placed in one step, and epoxy cured in one step, a significant time savings would be realized. This is especially true if each die must be aligned accurately relative to fiducials on the other die. By putting multiple fiducials on a see-through bond head containing multiple individually controllable suction nozzles, several die may be picked up with high precision onto the bond head, moved to the substrate, and placed with high precision in a single step.